Automatic tightening devices, also known as tighteners for strapping cargoes are common in places where commodities are circulated and can strap stacks of cargoes transported by a vehicle together to avoid loosening during transportation and prevent damage of the commodities or occurrence of safety accident.
Currently, there are two kinds of automatic tightening devices in the market, one having rolling and unrolling control functions and the other having no rolling and unrolling control functions. A driving structure for automatic rolling is realized by the process of releasing a coil spring, and during the automatic rolling, long webbing is rolled up quickly and unimpededly, but a hook at an end of the long webbing is pulled back by inertia which causes jump phenomenon and relatively increases the rate of accidental injuries of operators or nearby people.
Therefore, the automatic tightening device with rolling and unrolling control functions is a main trend in the market. However, among the tightening device with rolling and unrolling control functions in the current market, some achieve their functions by being added with an unrolling stopping structure part, may easily misguide users under a load state, and have high cost, while some are not additionally added with an unrolling stopping structure part, but operations thereof are very complicated, which will certainly affect the operation efficiency and actual practicability.
How to reduce the rate of accidental injuries caused by automatic rolling while providing an automatic tightening device with rolling and unrolling control functions, which is operated conveniently and has a simplified structure and low cost, becomes the problem to be solved by the present invention.